Gear tooth bearings or slewing rings are typically used when it is desired to rotate a large or heavy structure relative to a stationary or non-rotatable structure. Slewing rings are commonly used in material handling attachments, such as demolition shear attachments, concrete crusher attachments, grapple attachments, and the like, which are adapted to attach to the boom or stick of an excavator. Slewing rings are also utilized on excavators for rotating the platform supporting the cab and boom relative to the undercarriage of the excavator. Other applications for slewing rings are also well known.
Slewing rings have an internal race which is supported by and rotatable relative to an outer race. The inner race is rotated relative to the outer race using a hydraulic gear drive which engages internal gear teeth of the inner race. The gear teeth of the gear drive and slewing ring must be regularly greased to reduce friction and minimize wear. However, because the gear teeth are circumferentially enclosed by the outer race and are enclosed at each end by the mounting plates or bulkheads which attach to the inner race and outer races, the gear teeth are inaccessible without removing one of the bulkheads or mounting plates.
One type of prior art grease assembly that has been used for providing grease to the internal gear teeth of the slewing ring of a swivel attachment for material handling attachments, involves drilling a hole through the bulkhead and tapping both ends of the hole with internal threads. A grease fitting is threaded into the tapped hole on the back side of the bulkhead and a bent steel or copper tube with a pipe fitting is then threaded into the tapped hole on the front side of the bulkhead. When the slewing ring is mounted to the swivel house and to the material handling attachment, a grease gun can be placed over the grease fitting on the back side of the bulkhead and grease can be pumped through the hole in the bulkhead and into internal tube which directs and delivers the grease to the internal gear teeth of the slewing ring.
While such slewing ring grease assemblies serve their intended purpose, they often fail over time because the internal tube and/or pipe fitting unthreads from the tapped hole due to vibration and rotation of the material handling attachment during use. Once unthreaded, the internal tube will fall inside the slewing ring and will get crushed between the gear teeth as the material handling attachment is rotated, which can result in damage and/or increased wear of the gear teeth. Additionally, without the internal tube in place, grease cannot be properly directed and delivered to the gear teeth, resulting in increased wear and decreased life of the slewing ring. Furthermore, it should be appreciated that the internal tube cannot be recovered and replaced without removing the slewing ring from the swivel house, resulting in considerable down-time.